msm: mdss: add support for dynamic refresh in clock update method

It is possible to change the refresh rate of the panel by
changing the byte clock and pixel clock to the required panel supported
frequency. This change adds support to program dynamic refresh
registers and trigger the dynamic refresh interrupt. Once the current
frame is done, hardware ensures that the change in clock frequency is
taken effect within the vertical blanking period.

Change-Id: I3a1e0eb478c34111e94f977088c20e9a50c4ef25
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>